When a front working implement having a bucket, fork or like working portion at the front ends of a pair of opposed booms is to be attached removably to the body of a vehicle, the lower ends of a pair of opposed masts supporting the booms and the front ends of a pair of opposed braces projecting forward from the masts are usually removably connected to bearing portions provided on the tractor body.
For example, U.S. Pat. No. 3,949,889 discloses an arrangement wherein the lower ends of the pair of masts are adapted to be detachably fixed to the tractor body by removable pins, and the braces projecting forward from the masts are each provided at the front end with a hook which is fixedly engageable with a cam pin on the tractor body.
When this conventional arrangement is used for a front working implement the working portion of which is operated for loading, the connections between the implement and the tractor body are insufficient in strength, such that if the implement is advanced and retracted repeatedly, the connections are liable to backlash.
If the front portions of the braces are fastened directly to the mount portions on the tractor body with bolts, a shearing force acts on the bolts during work, possibly breaking the bolt.
Stated more specifically with reference to a case wherein the working implement is a front loader, a tensile force acts on the braces through the booms when the bucket is forced into sand or earth during work, while the braces are subjected to a compressive force when the bucket is retracted with earth placed therein, so that if each brace is merely fastened to the body mount portion laterally with a bolt, the bolt is likely to break.
To prevent the break of the bolt, there is a need to employ a complex structure, which nevertheless renders the working implement difficult to attach to or remove from the tractor body easily. Furthermore, the mount portions will become an obstacle in attaching other working implement to the tractor body to impair the versatile usefulness of the tractor.